Art of electromechanical recording of sound and in the photoelectric reproduction ofthe latter from the inscriptions obtained



July 13, 1937. BONNEA 2,086,934 ART OF ELECTROMECHANICAL RECORDING OF SOUND D IN THE PHOTOELECTRIC REPRODUCTION OF THE LAT R FROM THE INSCRIPTIONS 0 INED 24 53 2 ets-Sheet 1 F11 March 19 Fly! y my? R 7. i

July 13, 1937. T p. ONNEAU 2,086,934

ART OF ELECTROMECHANICAL RECORDI OF SOUND AND IN THE PHOTOELECTRIC REPRODUCTION OF THE LATTER FROM THE INSCRIPTIONS OBTAINED rch 24, 1935 Filed Ma 2 Sheets-Sheet 2 pzzmmm Patented July 13, 1937" ART OF ELECTBOMECHANICAL RECORDING OF SOUND AND IN THE PHOTOELECTRIC REPRODUCTION OF THE LATTEB FROM THE INSCRIPTIONS OBTAINED Paul Edmond Bonneau, Paris, France, assignor to Societe Anonyme La Recherche Industrielle Francaise, Paris. France Application March 24, 1933, Serial No. 662,597

In France March 31,1932

ZClaims. (cl. lie-100.4) I 1 ways presents irregularities such as I. If the The present invention relates to the art of electromechanical recording of sound which consists in forming a groove of constant width in a' film or'other carrier by means of a tool vibrating transversely to the direction of movement of this film. It also relates to the. reproduction or synthesis of sound from the grooves thus obtained.

The improvements forming the subject-matter of the invention 'have for their object to correctv the inconveniences of the known art and to apply to the latter new means fordeveloping the advantages of the same, particularly concerning the immediate reproduction of the phonograms obtained and the commercial repetition of satisfactory positives from proofs which are poor concerning high frequencies which, in electromechanical recording, give reduced amplitudes. Referring to the accompanying drawingsf Fig. 1a is an enlarged section of the cutting edge of a tool;

Fig. 1b is-a sectional view of a carrier with an opaque cutting showing one form of cut;

Fig. 1c is a sectional view of a carrier showing a second form of cut;

Fig. 2 is a sectionalview of a film constructed in accordance with the invention;

Fig. 3 is a fragmentary plan view of the film partially sectioned to show the groove or trace formed therein;

Fig. 4 is a diagrammatic view partiallyin section of the arrangement for guiding and operating on the film; a

Fig. 5 is a modification of the arrangement shown in Fig. 4,; v

Fig. 5a is a fragmentary perspectiveview showing the arrangement of the tool relatively to the surface of the mm;

Fig. 6 is an enlarged fragmentary view of an original negative film;

Fig. '7 isa diagrammatic view partially insection of a fllmfeeding apparatus provided with a photoelectric reading device;

Fig. 8 is a partial plan view of a form of film:

Figs. 8a. and 8b are transverse sectional views of different forms of film;

' Fig. 9 is a diagrammatic view partially in section of a printing apparatus;

i Figs. 9a and 9b are detail views of the recorded sbund; Figs. 10a and lot are sectional views through 'further forms of the film.

Fig. 1a shows how the cutting edge of the tool appears when Whatever may be the precautions taken for grinding and polishing this cutting edge, it alby a transparent ii an axis parallel to the seen through a microscope.

depth of cut is so adiusted asnot to cut into the carrier, the bottom of the groove will appear as shown in Fig. lb, with traces Z of opaque material adhering tothe carrier-3. If, on the contrary, the cut is so adjusted that no opaque trace remains, the bottom of the groove will have the shape indicated in Fig. 10 with serrations-l resulting from removal of the hard material of the carrier.

In order to remedy these inconveniences, the film used for recording purposes is constituted, according to the invention, by three, instead of two, elements arranged as indicated in Fig. 2. Between the superficial opaque material 5 and the transparent carrier 3, which can be as hard and resistant as necessary, is interposed a layer 5 of a transparent, softand but slightly resistantmaterial capable of being easily cut by the tool. i

This layer 6 can be of small thickness. It

will however be at least equal to the error possible in vertically positioning tool.

The said layer 8 will be constituted, for instance, by a soft gum, a fatty varnish, a gelatine but slightly resistant. It can also be constituted material, relatively hard at normal temperature, capableof rapidly softening at a higher temperature, under the influence for instance of heat locally concentrated on its surface.

The opaque layer 5, the thickness of which is preferably as small as possible, can be obtained either by spreading a suitable material, or by deposition, of a pulverulent body, or by inking the'surface of the layer 6., or by the .use of a dye v the solvent of whichwill penetrate but very the cutting edge of the manner that the cutting edge of the tool has to material of the layer 6, the hard material of the out only into the soft without ever reaching carrier 3. Thus, less energy will be required from the device actuating the tool.

The transparent groove formed by the tracing tool in the opaque material is in the form indicated in Fig. 3. The trace 1 of the cutting edge is limited by two identical lines 8 and 9 constituting the oscillographic image of the vibration. In is the median axis of the groove and latter at a distance at least equal to the greatest amplitude recorded.

It has been suggested, for reconstituting in sounds the wave recorded, either to remove, by

a planing action, the opaque regions comprised between the axes I and II, or to cover the same region by means of a screen arranged in the In fact, it is known that one of the simplest forms light rays striking upon -of this device comprises a very narrow slit,

brightly illuminated, and provided in a diaphragm, an objective having a very short focus transversely forming a real image of this slit on the record of the sound film, for instance at l2. The boundaries of the horizontal edges of this beam of light are, necessarily, perfectly fixed, and the same is true for both ends of the said beam.

A correct reproduction of the sounds will be obtained without having to eliminate or to cover the region comprised between the axes ill and II, by displacing the luminous trace in such a manner that one of its ends should come, as indicated at l3 or H on the median axis ID, or, at least, at such a point that the beam It or I is always intersected by one only of the record lines 8 or 9.

It will be understood that, if a is not possible to displace the light beam of photoelectric devices in reproducing apparatus, the same result will be obtained by adjusting the location of the record so as to maintain the arrangement indicated at l3 or I. This will only be possible, for standard positive sound films, provided recording is effected on the original negative film by slightly overlapping the place where the perforations are formed, this necessitating the use of a film perforated on one side only. v

By arranging the sound trace at ll rather than at l2, the noisecaused by the reproduction will be materially reduced. In fact, it is known that this noise is, for the greater part, due to the perturbation of the luminous fiux impressing the cell by the multiple opaque imperfections of the carrier, through transparent regions of the rec- 0rd.

When the opaque regions comprised between the axes Ill and II are eliminated and the reading is efiected by means of the beam 12, the latter uselessly illuminates the transparent region located at the right-hand side of the axis ll, whereas the beam l3 only illuminates the emcient transparent regions of the oscillography.

The recording apparatus for carrying out the known process, comprises an electromechanical receiver converting the amplified microphonic currents into vibrations of the recording tool and a set of mechanisms, film a strictly uniform and to ensure -a rational formation of the oscillographlc groove.

.The invention is particularly adapted to ensure:

(1) Correct guiding of the film.

(2) Accurate adjustment of the depth of penetration of the tool into the material.

(3) An adjustment allowing the cutting edge of the tool to be placed parallel to the surface to be cut.

mechanical receiver allowing utilization of the entire width of the film. v

,The provision of a photoelectric reading device which can be used for controlling the recording operation at the verymoment it is effected.

adapted to impart to the, movement of translation (4) A reciprocating movement of the electro- Fig. 4 diagrammatically iliustrates the device for guiding the film and, on an exaggerated scale the device for adjusting the depth of cut. The film l5 unwinding from the distributing magazine passes a curved gate constituted by a fixed part I6 and a door I! movable about an axis l8 parallel to the generatrices of the curvature of the gate. The film is pressed against the gate by a roller l9 and is driven by a toothed cylinder 20 towards the receiving magazine.

10 The film is laterally guided according to a classical device, not shown in the figure, on one side by a fixed ledge of the gate and acting as an abutment, and, on the other side, by a fiat spring or by the cheek of a spring roller which pushes it towards the abutment.

By conforming to the curved shape of the gate on which it is firmly pressed, the film cannot warp or be lifted, which result could not be obtained with a plane gate.

.. The adjustment of the depth of cut is obtained by maintaining a constant distance between the cutting edge of the tool and the outer face of the film. For that purpose, the door l1 of the gate which is movable about the axis I 8 tends to rise under the action of a counterweight 2|, until itabuts against a perfectly polished guide 22, rigid with the electromechanical receiver 23. This guide is located as near as possible in front of the tool 24 and slightly to one side.

Its level can be exactly adjusted by means of a micrometric screw 25 and by distorting more or less the member 26 on which it is secured. It will be understood that the illm, held between the guide 22 and the door I! is penetrated by the tool to a depth exactly equal to the difference between the relative positions of the cutting edge and the lowest point of the guide 22.

The member 26 can of course be replaced by any system allowing slight vertical displacement of the guide 22, and the counterweight 2| can be replaced by springs the tension of which is adjustable.

For that purpose, the guide 22 will be allowed a certain freedom of movement in the vertical direction, by placing for instance the head of the screw 25 no longer vertically above the guide, but at a point sufiiciently distant from the supporting member 25, at '21 for instance. The

member 26 must be but slightly resilient in order that to a very small vertical displacement of the guide should correspond a considerable increase of the pressure it exerts on the door H. In these conditions, the moment of the reaction of the cutting edge of the tool is equal to the difference 9 between the moments of the forces of gravity acting on the member l1 and the moment of the force applied at 22. The latter being proportional'to the level, the reaction of the tool decreases when the penetration-of the cutting edge increases and the leverage of the force 2| can be adjusted in such a manner that it is annulled for a very small depth, or at least in order that the tool should be pushed back as soon as it encounters a slightly abnormal resistance. r

Fig. 5a shows how the-cutting edge of the tool 24 should be placed relatively to the surface of the film IS. The cut can be considered as correct when a shaving 28 of uniform thicknessis obtained. Consequently, it is necessary that the parallelism of the cutting edge of the tool with the surface of the film should be correct. For that purpose, the electromechanical receiver 23 will be carried by a support 29, with some freedom The standardized characteristicsof the und film require that the oscillographic recording of the sound should be effected in a. narrow strip located on one of the sides of the film, for instance at 32 in Fig. 6, which shows an enlarged fragment ofan original negative film. It is known that, for printing the positive film, this region 32 alone is used, the remaining surface being covered for reserving the space required for the images. It is therefore possible, for other purposes and without diminishing the valueof the negative which can still be used for printing standard positive copies, to use the remaining surface for other sound. records such as 33, 34, 35, etc. It is thus possible to place, in the width of a film of 35 m. m., seven or eight sound records of 2,5 m. m. in width, or a much greater number if recorded amplitudes of less importance are omitted.

. These supplementary records will be used either by way of trials for repetitions, or for applications which do not include the simultaneous use, on one and the same film, of kinematograp hic images. It will moreover be understood that it is possible to photographically transfer a negative record such as 34, on a positive film, at the standard location corresponding to the record 32, by effecting printing, not by contact, but in an optical printing apparatus the objective of which is combined with parallelepipedon-shaped lenses.

In order to obtain multiple records on the film,

the electromechanical receiver will receive a movement of translation parallel to the transverse axis 36. i For that purpose, a rest diagrammatically indicated at 31,.is provided for slidably supporting the support 29.

It is very important that the operator recordin the sounds should be able to ascertain, when effecting this operation, the quality of the record.

It has been previously indicated how it is possible to photoelectrically reproduce the records obtained in the film without having to plane one of the sides of the oscillographic groove, and that it suffices, for that purpose to place on this groove the light beam of the optical system in the manner described. According to the invention the feeding apparatus is provided with a photoelectric reproducing device, diagrammatically illuscomprismg a lamp 33, a microscope lens system 39and a light-sensitive cell 43. The light beam 4| is directed-on the surface of the film, and the light rays have access to the cell through a transverse slit 42 in the curved gate l6 and as near as possible to the point 31 .of engagement of the tool and behind the latter in the direction of the movement.

' The operator will listen to the electro-acoustic reproduction of .In order to be able to reproduce the various. records 32, 33,.etc., the device, 38, 33, 4t. is.

mountedfor movement parallel to the axis 36. This movement can of the electromechanical receiver, with three degrees of freedom corresponding to three different is given the locations l2, [3 or l4 or Fig. 3.

the microphonic currents gene erated by the cell 40. He will thus hear the result be synchronized. with that modes of reproducing according as the light beam Fig. 1c shows on an enlarged scale the irregularities of the bottom of the groove of the record owing to the unavoidable imperfections of the cutting edge of. the tool. I The serrations such as 4 give rise, as shown in plan view inli'ig. 8, to striae 43 having the shape of the record line 44 of the groove- When the film is fed in the direction of the arrow 45, opposite the illumi-i hated slit of the photoelectric system, these striae modulate the light beam passing through the transparent region of the groove and this causes, in the reproduction of the sounds, intense parasitic noises. If the original film thus formed is used for the printing of a positive copy, this printing photographically takingplace by means of directed light, the same striae 43 will refract the light passing through them and will produce, on the copy of the groove, two sinuous lines which will undesirably affect the sound reproduction.

For avoiding this inconvenience, a thin layer of varnish is, according to the invention, spread in the bottom of the groove, this layer of varnish presenting, as exactly as possible, the same index of refraction as the cut transparent material. a l

Fig. 8a is a section of a groove with the irregular'ities 46 resulting from the striae43,'and Fig. 8b shows the same irregularities embedded in a layer 41 of transparent varnish. The outer surface of this layer being smooth, and the whole 41, 48 being optically homogeneous, there is no longer any possibility of refraction of light through the transparent regions of the groove. Besides, the deposition of thelayer' 41 has for effect to protect the edges 49 of the groove.

A varnish having the same index of refraction as the material 48 will easily be obtained by preferably dissolving the material in a very volatile liquid. The application of the layer 41 can be automatically effected by means of a machine combined with a drying apparatus.

The electromechanical device actuating the recording tool having a non-negligible inertia, the amplitudes of the curve recorded on the film are, for one and the same intensity of the telephonic current actuating the receiver, reversely proportional to the frequency. Therefore the high frequencies of the voice which serve as a structure for articulated language tend to be sacrificed in oscillography.

The means described hereinafter which are included in the scope of the invention, are adapt-'- ed to remedy this inconvenience.

It will be assumed that by means of a recorder provided with the improvements above described,

the oscillographic groove of Fig. 6 has been recorded, this groove bearing the record of high frequency vibrations the amplitude of which is insufficient. It will also be assumed that, by

causing the film to move againthrough the matween the cell 40 and the receiver 3|, an ampli-. fier the coefficient of amplification of which is proportional to the nth power of the frequency, 11 being greater than 2.

A second means is available, which can moreover be usefully combined with the first one. This second means consists in effecting the re.-recording, no longer at the standard speed of movement of the" sound film, but at a much slower speed. This is equivalent to transposing the musicai scale of the record 34, that is to say to acoustically reproduce it in a much lower tone than the natural tone. It will be assumed, for instance, that the film moving device receives a. linear speed of 114 millimeters per second, whereas the standard speed at which the inscription 34 was obtained was of 456 millimeters, the vibrations inscribed at 34 at a frequency of 2,000 for instance, will occur at 32 at a frequency of 500, that is to say in a region of the frequency scale for which the electromechanical receiver is sixteen times more sensitive than in the first case. In fact, the advantage of the method resides in the use of much lower speeds, such that, whatever may be the vibrations inscribed at 34,

the receiver is statically actuated and no longer dynamically actuated. In these conditions, the amplitudes of the records engraved by the tool remains independent of the frequency and the law of the amplitudes re-recorded in function of the frequency can easily be controlled by the use of suitable equalizing circuits in the amphfier. i

It is known that tifis extremely difilcult to feed at a very slow uniform speed, without jerks and vibrations, a kinematographic film driven by its perforations.

This difiiculty does not arise here in the method forming the subject-matter of the present invention. In fact, the photoelectric reproduction and the re-recording taking place simultaneously and conjointly on the same fi1m,the variations of speed of the latter are' without action on the desired result. This advantage constitutes the essential difi'erence existing between the present invention applicable to the process for recording on films and the similar methods which have already been suggested for' transferring on a phonographic wax record the oscillographic inscriptions photographically obtained on a film.

For electromechanical recordingin a material the resistance of which is negligible it is necessary that the receiver should be supplied with an energy which is proportional both to the square of the frequency and. to the square of the inscriber amplitude. It is also known that electromechanical and electro-acoustical devices respond to the impulses which are transmitted to them so much the more accurately and'without distortion as the energythey transform is smaller.

'It results therefrom that, in the application of the means according to the invention, it is very important to limit to a fewtenths of a millimeter the amplitudes of the recorded sounds.

Now, the standardized requirements of sound films necessitate a positive copy bearing a recording of the sounds the amplitudes of which appreciably exceed one millimeter in the forte.

The means described hereinafter allow. according to the invention, to remedy this compromise and to obtain, by photographic printing, a positive copy with large amplitudes from an original negative with small amplitudes.

Thismethodcanbecarriedoutowlngtothe fact that the process for 'cording on films such as described affords oscillographic grooves presenting an absolute contrast between the opaque regions and the transparent regions. The same method is not to be recommended for the enlargement of photographic recordings of fixed density the opac ities of which are never absolute and the transparencies are imperfect. It is also to be noted that the means described hereinafter relate to the general enlargement, according to one and the same ratio, of all the amplitudes of the inscription and must not be mistaken for the process described above which, by way of electrical re-inscription, affords a selective enlargement of the amplitudes in function of the frequency.

Use is made of an optical printing apparatus, of the type commercially used for printing copies of kinematographic films, the principle of this optical printing apparatus being diagrammatically shown in Fig. 9. An original negative film 50 unwinds, with a continuous movement from a dis- I tributing magazine 5| towards a receiving magazine 52. It passes in a gate 53, the aperture of which is brilliantly illuminated by a lamp 54 provided with a suitable mirror and condenser. The nonrecorded positive film 55 which is to receive the impression is arranged opposite and unwinds parallel to the film 50, at a precisely equal speed. Between both apertures 53 and 56 is arranged an objective 51 forming on the nonrecorded film 55 a very sharp image of the sounds recorded on the film 50.

The invention, in a first modification, consists in replacing the spherical objective 5! by a cylindrical objective giving, in a plane at right angles to the displacement of the -films a greater enlargement than in the plane of the figure.

It results therefrom, for instance, that a line, such as 58 (Fig. 9a), recorded on the film 50, will produce on the film 55 an image 59 in the form of a line of the same thickness or of smaller thickness and of greater length. It will be understood that, by this means, it is possible to enlarge the amplitudes without impairing the accuracy of the record, that is to say without diminishing the definition of the frequencies.

In a second modification, the objective 51 is a spherical objective. of the same type, but giving a greater enlargement and which is combined with .a very thin slit arranged at right angles to the plane of Fig. 9 and allowing only a very narrow portion of the light bundle issuing from the objective to reach the film 55.

Fig. 9b atically shows, the formation of the image. Let 50 be a curve traced on the II and having, 'for instance, amplitudes of 1 6 of a millimeter. given a magnifying power sufilcient for obtaining on the film 55m image such as 5|, enlarged, for instance, ten times, and presenting consequently amplitudes of one millimeter. If the film 55, was moving at a speed ten times greater than that of the film 55, the curve 5| would be obtained on its surface, without using anyother contrivance. If, on the contrary, a very narrow light bundle when issuing from the objective, through a slit 5! of two or three hundredths of a millimeter is allowed to reach the film 55 and,

if on the other hand, the film 55 is compelled to move at the same sped as the film 50, a curve such as 63, will be impressed on this film II,

which curve 53 is the exact reproduction of the The objective is It will be understood that the slit 62 can be arranged at any other place on the axis of the optical system of Fig. 9, for instance very near the film 50. This slit moreover, can be chosen higher than is necessary, the image of the original inscription can be formed in its plane with a first spherical objective, and the said image can be projected by a second objective, with a suitable enlargement, on the film 55. r

Both modifications which have just been described can moreover be combined, and the slit 62 can be replaced by a cylindrical objective.

Processes are known allowing to print on a paper ribbon or on any other support the oscillographic records of fixed density photographically obtained on an original film. This printing is effected by means similar to those used for the reproduction of drawings.

The invention permits simplifying thisv printing method, which simplification is applicable to the transfer of the oscillographic records obtained, as above described, in the superficial layer of a film.

' Fig. 10a is a section of an oscillographic groove 65. The groove being engraved, itwill be understood that it is easy to fill it with printing ink, at 66. After wiping the surface 61, the film will be pressed against a paper ribbon, the contact being obtained between two cylinders similar to those of a rolling mill, one of these cylinders being lined with felt.

Reversely, the film being superficially constituted' by a material having a high afilnity for printing ink, the regions in relief alone will be inked by means of a roll, as shown at 68 in Fig. 101). In this case, it is desirable that the bottom of the groove 69 should repel ink.

For that purpose, it is convenient to constitute the film by means of three materials. having dif- 40 ferent properties and laid on each other: a carrier Ill which, for this application, need not be transparent, a slightly-resistant layer can be easily cut and having no affinity for printing ink, finally, a third material 12 capable of retaining the latter.

a groove which a final proof is constituted by a ribbon of opaque It will be understood that the transfer process diagrammatically shown in Fig. 10a will give on the final proof an .oscillographic groove black on a white background and that -shown in Fig. 10b is white on a black background. the photoelectric reproducing vary. It is known that if the In both cases, process will not .paper, it is possible by brilliantly illuminating the latter to influence, by means of reflected light, a

photoelectric cell.

The presentinvention also relates to the reproduction of the same paper ribbon, no longer by reflection, but by trai'isparencyt by using 'for illu L. passage, in

minating the oscillographic groove a source of light, rich in rays of short wave length, combined ,with a photoelectric cell responsive to these radiations only.

A paper ribbon of transparent and it is always possible to brilliantly illuminate it with white light so that a photoelectric cell can be impressed, through the thickness of the said ribbon, and allowing this cell to reveal the opaque designs printed on the surface.

But it is difficult and costly to obtain a paper pulp sufiiciently homogeneous in order that the w ,front of a cell, of the transparent \regions of such a ribbon should not give rise to parasitic impressions determining, upon reproduction-\of the sounds, a wheezing noise.

small thickness is sufiiciently For re edying this inconvenience, use will be made of a light rich, for instance, in ultra-violet a great transparency and concerning which the lack of homogeneity of the pulp, provided the latteris pure, is negligible. Moreover, the proc- 'ess diagrammatically shown in Fig. 10b will preferably be used, this process giving a smaller transparent surface than the process shown in Fig. 10a. The printing ink used willbe loaded withmetallic salts presenting a great opacity relatively to ultra-violet rays. A photoelectric cell responsive to these raysonly will be employed, or, preferably, regions of the spectrum including ultra-violet, combined with a selective coloured filter allowing these latter radiations only to pass,

What I claim as my invention and desire to secure by Letters Patent is:----- 1. In an apparatus for recording sound, a film support, a sound recording cutter and means to means for reproducing the recorded sound on the portion of the film passing over said opening.

2. In an apparatus for recording sound, a film support, a recording, cutter arranged adjacent the support, means for transversely displacing the said cutter from one position to a second position, means to operate the cutter in accordance with sound when the cutter is'in the first position, the support with the sound record produced by the cutter in the first position and located immediately following thereto, a circuit including an amplifier for operating the cutter when the said cutter is in the second position, and means for controlling said circuit by the portion of the film passing over the opening.

PAUHaEDMOND. BONNEAU.

a cell responsive to all the having an aperture in line 

